I re-checked the traction idler pulley, and it was tight. I took off the swing plate just to make sure the traction disc pulley was ok, and it was very good. Then, while I had the swing plate off, I decided to fabricate a belt keeper for the traction belt. I took a metal rod and attached it to the bottom of the swing plate, and it rotates toward the pulley to, hopefully, keep the belt on the pulley. Ariens does something similar as a belt keeper. Then I gave it a garage-test (pouring rain) with the wheels off, and went through about 5 minutes of test. It isn't conclusive, but the belt stayed on.
Attached a a few photos that you requested - the first two are looking down the pulley area with the traction disengaged. Then I took the same two with the traction disengaged. Then there are some with various angles of the belts, and also one of my belt keep, and the final one show to double pulley. The last one was interesting because it shows how the traction belt seems to sit very deep within its crank pulley. It seems like a wider belt would sit better (higher) in the pulley, but it is a factory belt - I think 3/8". Seems odd, to me anyways ! I apologize because the photos don't seem all that good or telling. I may try to get better pictures tomorrow if you'd like.
Again, thanks for your expertise, and my apologize to others for using bandwidth.